Possibly LoganStrohl's sequence Intro to Naturalism. The sequence describes his attempts to "know the territory... [by] patient and direct observation". I tried doing one or two of the activities he describes and I thought they were communicating something useful about how to become curious about reality. But you'd have to do some work into converting these into multi-person activities.
Note that I haven't read and understood the whole sequence, so my suggestion will be worse than what you'd generate by reading and thinking about this yourself. But I'd suggest looking at some piece of reality and trying to figure out why it is the way it is. Say, look at a household object and see if you can tell what makes it well (or poorly) designed. Or perhaps read a paragraph by a mutually beloved writer and analyse it to see why they wrote it the way they did. Or look at a proof by a terse mathematician (like Rudin) and see if you can come up with a quicker or more elegant proof. If not, why not? Focus on a curiosity generating activity and let the conversation be guided by discovery.
I'd focus on noticing the Soldier mindset ("arguments as soldiers"). Find a personal "cherished belief" that would be really hard to let go of, and have your partner poke at it. Not a token belief, but a real one. Then notice your emotional state and the inner need to fight for it. That's the mental state one wants to remember, "but I am right and this is true!" and notice when it happens in other situations.
I'm thinking about doing a LessWrong meetup around the Scout mindset. I prefer to have meetups where there are a lot of two-person exercises as those are really good to get nerds who have trouble with normal small talk to connect to each other in addition to often also being useful for developing skills over lecturing the whole time. Can anyone think of good exercises that could be done at a Scout mindset meetup?